Browsing by Author "Pflug, Beth R."

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    Metabolic and Molecular Regulation of Dietary Polyunsaturated Fatty Acids on Prostate Cancer
    (Wiley, 2016-03) Zhao, Heng; Pflug, Beth R.; Lai, Xianyin; Wang, Mu; Department of Biochemistry & Molecular Biology, IU School of Medicine
    Purpose The aim of this study is to investigate the role of n-3 and n-9 fatty acids in crucial processes involved in prostate cancer cell growth through a large-scale proteomic analysis. Experimental design We used a label-free protein quantification method to profile global protein expression of fish oil and oleic acid treated PCa cells and validated a panel of differentially expressed proteins by either Western blot or multiple reaction monitoring. Bioinformatic analysis was also performed to uncover the pathways involved in fatty acid metabolism. Results Fish oil, not oleic acid, suppresses prostate cancer cell viability. Assessment of fatty acid synthesis pathway activity also shows that oleic acid is a more potent inhibitor than fish oil on de novo fatty acid synthesis. Although fatty acid synthase activity decreases with fish oil treatment, the inhibition of its activity occurs over time while reduction in viability occurs within 24 h. Bioinformatic analysis revealed the pathways altered by these fatty acid treatments. Conclusions and clinical relevance This study suggests that suppression of cell viability by fish oil is independent of fatty acid synthase and fish oil regulates prostate cancer cells through activation of other pathways depending upon length of exposure to fish oil.
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    Molecular mechanism of orlistat hydrolysis by the thioesterase of human fatty acid synthase for targeted drug discovery
    (2014) Miller, Valerie Fako; Zhang, Jian-Ting; Jerde, Travis J.; Liu, Jing-Yuan; Pflug, Beth R.; Pollok, Karen E.; Safa, Ahmad R.
    Fatty acid synthase (FASN) is over-expressed in many cancers, and novel inhibitors that target FASN may find use in the treatment of cancers. It has been shown that orlistat, an FDA approved drug for weight loss, inhibits the thioesterase (TE) of FASN, but can be hydrolyzed by TE. To understand the mechanisms of TE action and for designing better FASN inhibitors, I examined the mechanism of orlistat hydrolysis by TE using molecular dynamics simulations. I found that the hexyl tail of orlistat undergoes a conformational transition, destabilizing a hydrogen bond that forms between orlistat and the active site histidine. A water molecule can then hydrogen bond with histidine and become activated to hydrolyze orlistat. These findings suggest that rational design of inhibitors that block hexyl tail transition may lead to a more potent TE inhibitor. To search for novel inhibitors of TE, I performed virtual DOCK screening of FDA approved drugs followed by a fluorogenic assay using recombinant TE protein and found that proton pump inhibitors (PPIs) can competitively inhibit TE. PPIs, which are used for the treatment of gastroesophageal reflux and peptic ulcers, work to decrease gastric acid production by binding irreversibly with gastric hydrogen potassium ATPase in the stomach. Recently, PPIs have been reported to reduce drug resistance in cancer cells when used in combination with chemotherapeutics, although the mechanism of resistance reduction is unknown. Further investigation showed that PPIs are able to decrease FASN activity and cancer cell proliferation in a dose-dependent manner. These findings provide new evidence that FDA approved PPIs may synergistically suppress cancer cells by inhibiting TE of FASN and suggests that the use of PPIs in combinational therapies for the treatment of many types of cancer, including pancreatic cancer, warrants further investigation.